so·ste·nu·to 
(sō′stə-ntō, sô′-) Music
(sō′stə-ntō, sô′-) Music adv. & adj.
In a manner that is sustained as long as or beyond a note's full value. Used chiefly as a direction.
n. pl. so·ste·nu·tos or so·ste·nu·ti (-tē)
A sostenuto passage or movement.
[Italian, past participle of sostenere, to sustain, from Latin sustinēre; see SUSTAIN.]